You might like to read up on speculative evolution. A lot of it is much wilder than your example, but when experts get into it as a form of fiction, the results are lovely. This project is neat. https://sites.google.com/site/worldofserina/
On the other end of the scale, “exactly like an existing bird, but it has a slightly different coloration and lives in a slightly different area” is a viable species. Or, thousands of species.
When I first joined iNaturalist, rhinogrades were still part of the official iNat taxonomy!
They were first described in 1954 in the monograph “The Snouters: Form and Life of the Rhinogrades.” I got it from the library, it’s a fun read. It’s now available online at https://archive.org/details/snoutersforml00stum
There’s a few books about topics like this. Arguably the most well know is After Man: a Zoology of the Future by Douglad Dixon and it “documents” what type of animals may evolve millions of years into the future, long after mankind ceases to exist. It comes fully illustrated and all! My favorite animal is probably the Pamtret (Vulpemustela acer), a type of maned, cougar sized mustelid descendant from weasels. Some of the animals described there seem a bit too out there for me personally, but many could easily exist in our world today (like the rabbuck, camelid-looking animals descendant from rabbits).
I’ve been wanting to get my hands into a paper copy for years but alas, there doesn’t seem to be anyone selling it in my country.
Also, @edanko that bit of trivia about rhinogrades and iNat is both hilarious and cute. Do you know if it was added as a mistake or was it perhaps a joke? Still, would love to see the classification iNat gave the rhinogrades, probably extinct?
We had a copy of “After Man” in my house when I was a kid. I must have read it in detail a few dozen times. Now I haven’t seen it in decades, and I can remember all the pictures but none of the names.
Darn, that’s what I call lucky!! I’ve contacted a few places that I get my biological and naturalist books from, as well as a few big libraries but they don’t seem to have it or even know about it sadly. Guess I will have to enjoy it in pdf form for now, haha
I had to go look in my home library and couldn’t find my book about the fictional Snouters (Rhinogrades) which came out in paperback in the early 1980s. I recall that one of my colleagues at the time, a biology graduate student who was taking his comprehensive exams for his PhD, was asked by his exam committee about Rhinogrades (presumably as a joke) and he was totally stumped. I had to laugh as I was reading the book at the time.
There’s also a Japanese documentary about After Man, using stop-motion creatures. I have never been able to find a subtitled or dubbed version, though: https://www.youtube.com/watch?v=eMxIFZNx1YY